Power drop-off at extremes of FT-8 passband

Phil N3ZP

I have read on several Flex forums not to use "Fake It" in FT8 for frequency control in WSJT-X because the Flex filtering is flat across the audio passband. I usually notice a slight power drop off at the low and high extremes. I am using a 3K filter width and run DIGU. Is this normal and possibly caused by the DAX driver or WSJT-X?

Larry _ NY8T

Just open your TX filter a little more, I use 0 to 4.5 Khz.

Phil N3ZP

Thanks, I'll try that.

Tim - W4TME

@Phil N3ZP I use "Fake it" all the time except when I am on 60m. It keeps the transmit signal in the middle of the TX filter and there is no latency degradation either. If the tones are really low in frequency, you are losing signal strength because it take more RF energy to transmit a low frequency tone than a higher frequency tone.

Phil N3ZP

Thanks, Tim. It makes sense now that you say it that a low tone needs more RF.